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Nutritional management of acute and chronic equine laminitis

Laminitis is an important equine disease, with evidence of its significance going back to the beginning of recorded history. Today, laminitis is said to be the most common reason for a horse to be presented for veterinary treatment, with an overall incidence of about 2 percent in the United States.1

Grazing danger: The type of pasture a horse consumes could play a role in the development of laminitis. (PHOTO: JOHN KELLY/GETTY IMAGES)

Laminitis, also known as founder, is a systemic disease that manifests in the foot acutely as severe pain and inflammation, lameness and debilitation. Regardless of its trigger, laminitis in its most severe form causes a breakdown of the laminar attachment, resulting in separation and movement of the coffin bone. As the coffin bone rotates and descends within the hoof capsule, the prognosis for recovery worsens. The disease begins with an initiation point and proceeds through a developmental stage before the acute phase of excessive laminar inflammation. Total destruction of the hoof structure can occur, depending on the degree of inflammation and the extent of laminar tissue damage. In its chronic form, laminitis can result in complete digital collapse or repeated episodes of founder.

Changes to the foot are theorized to be due to a disturbance of blood flow to the region as a result of an inflammatory mechanism from toxic, metabolic or enzymatic effects or from traumatic or mechanical factors. The final common pathway is thought to be one of mediation of extreme inflammation within the hoof capsule that eventually damages the laminar tissue severely, leading to detachment of the coffin bone. Possible contributors to the development of laminitis include endotoxemia, glucocorticoid administration, endocrine disturbances and excessive concussion on the structures of the foot. Additionally, various nutritional factors have been linked to the initiation and recurrence of the disease process.

Nutrition and initiation of the disease

According to the National Research Council (NRC), several factors have been implicated in the etiology of acute laminitis.2 Nutrition-related factors include excessive ingestion of rapidly fermentable carbohydrates (i.e., starch, sugars or fructans) as a result of overfeeding cereal grains, excessive intake of lush pasture or bolus feeding of a commercial fructan (inulin). Intake of black walnut shavings, insulin resistance and obesity have also been linked to the development of laminitis.

"There are several nutritional laminitic models, but what they are actually doing to the horse is unknown — whether it's directly related to nutrition or an indirect effect is the question," says David Hood, DVM, PhD, Foot Diagnostic and Rehabilitation Clinic, Bryan, Texas.

Although several factors have been associated with the onset of laminitis, the exact mechanism by which these factors trigger laminitis is still unknown.